In the automotive industry there is an ever increasing demand in terms of reduction of the weight of motor vehicle component parts in order to reduce fuel consumption and exhaust emissions.
In order to reduce the overall weight of the wheel and, in particular of the rotating mass, in recent years hub bearing assemblies have been proposed having a rotating flanged ring made of two different materials, joined together in a single piece. In such rings, a tubular core made of a first material of high toughness, such as steel for bearings, forms the raceways, and a second, light material, such as a light metal, forms the remaining part of the ring, including an outer flange for mounting the wheel. See for example the patent publication WO 2008/147284 A1.
In some cases, the coupling between the steel core and the lighter flange is made by form coupling with interference. These couplings do not always prove to be long-lasting, especially after prolonged use. Indeed, the different coefficients of thermal expansion of steel and aluminium tend to cause the two materials to separate one from the other. In other cases, the coupling is obtained by moulding or casting the light material, for example an aluminium alloy, over the tubular steel core. To avoid or limit movements between the two materials, in rings of this type, the two materials are joined with complexly-shaped interface surfaces, so as to produce undercuts that behave as joints between the two materials. The costs of producing rings using this technology are rather high.